Re-hydrating Dry Yeast

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elollerenshaw

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Do you need to re-hydrate dry yeast for the same reasons that you do liquid yeast?

It's probably a good practice, but is it as important?

Apologies if this has come up before, I haven't had too much success with the search function.
 

Wimmig

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As per the design of dehydrated [dried] yeast, it is designed for direct pitching. I am sure there are many people on both sides of the fence. I, myself, rehydrate dried yeast with a stir plate prior to pitching. Call it overkill, but it only cost $15 to make, so whatever. Prior to the stirplate i just pitched into a pint [glass] of water, and left it for an hour covered in foil.
 

barls

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i believe it was jamil that did the research when he was writing his yeast book. the figures is that sprinkling kills 50% of the yeast where as rehydrating only kills 5%. this is supported by looking at the instructions on the dried yeast manufacturers website in the home brewers vs the professional brewers destions
 

Yob

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Whats the safe temp range for not getting thermal shock when pitching / rinsing / rehydrating yeast?

Safale says + or - 3'c when rehydrating.. Is it the same when pitching to the wort? Thats the scale ive always used really and i dont know where i got it from..

I also add wort to my rehydrated yeast over 20 mins to get it within that 3'c range of the FV

Cheers
 

DUANNE

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i usualy use 30 degree or so water to rehydrate wich ends up at room temp give or take after 30 mins to equalise with my cube to hopefully avoid thermal shock. on lagers i have the cube in the ferment fridge to get a good temp for pitching so give the yeast 15 mins or so on the bench before putting in with the cube in the fridge to equalise with the cube before pitching.dunno how well it works compared to pitching straight on the wort tbh i still get much better results with liqued yeast so very rarely bother with dried but when i do use dry this is how i do it and get the best results i have with dried so far.
 

dr K

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Clearly you do not have to re-hydrate liquid yeast!!
Dried yeast ahs two disadvantages, first off there are only a small number (albeit very good) strains and second that some retailers may choose to buy in blocks and repackage.
With a liquid yeast a starter is always advisable, ideally it should be at the very least constantly stirred either by stir palte or airstone/filtered air, this not only introduces oxygen but drives off potentially threatening CO2.
Good quaility dried yeast (in Australia Fermentis and Danstar) are full of extra reserves , glycogen and trehalose to help the yeast kick off.
Rehydration is a good idea, its quick and easy and ensure greater greater viability, just remember than tough as laeather died yeast is still very tender in the initial minutes of pitching into your water only please rehydration cup or flask. Its a bit Rip van Winkle and during hat early stage the cell walls have a bit of a security problem. The ideal RH temp is around 40C, work on pitching about 20 minutes later (you are rehydrating not making a starter).
Fresh factory packed yeast will still be OK direct pitched despite a substantial kill rate from wort sugars hitting the unhydrated cell walls as well as the less than optimum temp.
Simple answer, take the yeast out of the friddge about an hour before you want to pitch and put it your shirt pocket, twenty minutes before you want to pitch get some 40C tap water in a clean flask and tip the yeast in, give a good stir to prevent clumping then let it get ready to rock! Pitch.

K
 

pcmfisher

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Clearly you do not have to re-hydrate liquid yeast!!
Dried yeast ahs two disadvantages, first off there are only a small number (albeit very good) strains and second that some retailers may choose to buy in blocks and repackage.
With a liquid yeast a starter is always advisable, ideally it should be at the very least constantly stirred either by stir palte or airstone/filtered air, this not only introduces oxygen but drives off potentially threatening CO2.
Good quaility dried yeast (in Australia Fermentis and Danstar) are full of extra reserves , glycogen and trehalose to help the yeast kick off.
Rehydration is a good idea, its quick and easy and ensure greater greater viability, just remember than tough as laeather died yeast is still very tender in the initial minutes of pitching into your water only please rehydration cup or flask. Its a bit Rip van Winkle and during hat early stage the cell walls have a bit of a security problem. The ideal RH temp is around 40C, work on pitching about 20 minutes later (you are rehydrating not making a starter).
Fresh factory packed yeast will still be OK direct pitched despite a substantial kill rate from wort sugars hitting the unhydrated cell walls as well as the less than optimum temp.
Simple answer, take the yeast out of the friddge about an hour before you want to pitch and put it your shirt pocket, twenty minutes before you want to pitch get some 40C tap water in a clean flask and tip the yeast in, give a good stir to prevent clumping then let it get ready to rock! Pitch.

K
Just wondering why you say 40 deg when Saf say 27 +- 3?
 

Fourstar

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Too long to retype so i'll re-quote.

In short. not re hydrating you can potentially loose up to 50% of your cell count. Not to mention fermentis packets only have 69 billion cells per packet compared with liquid cultures @ 100 billion cells.

slightly :icon_offtopic: but highly relevant.

im sure they handled their yeast and more so prepared it correctly too. :icon_cheers:

This isnt a dry yeast bash and you will see why. Dry yeast is completely fine assuming you handle it correctly and pitch it at correct rates.

I overheard some interesting information that Chris White (whitelabs) was discussing regarding the use of dry yeast. I believe he estimated cell death of dry yeast if not rehydrated of close to 50%. AKA pitching direct to fermenter.

Now using that information, see the following. The dry yeast packets state on their spec sheet each packet contains 11.5g of yeast and the viability at packaging is 6 * 10 ^ 9 (6 billion cells per g) which equates to 69 billion cells in a packet.

What do whitelabs and wyeast have as a starting point? Around 31% more viable cells in a fresh smack pack/vial. (wyeast state 100 billion cells, whitelabs between 70 -140 billion cells.)

Now the figures above are assuming you pitch the dry yeast after rehydrating. If not, that figure could be closer to 65% less yeast if you decide to sprinkle the dry yeast directly onto the wort.


Now if we think about correct cell pitching rates, what cell count do you need for a 1.050OG 20L wort?

750000*20000*12.5 = 187.5 billion cells.

At worst, one non-rehydrated dry yeast pack will get you to 18%~ of that recommended cell count.
one smack pack/vial assuming 100% viability of a liquid culture at 100 billion cells = 53% if your cell count.

I know what option i would choose.

Smack pack + 1L starter. For those fond of dry yeast, at least two rehydrated US05 packets. ;)
 

eamonnfoley

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Just make sure you water is sterile when rehydrating yeast. I once had a run of background infections that I think was from bacteria in my water filter.
Took me ages (eternity) to work out why my dry yeast beers were not coming out well. A quick 2 minute boil in the microwave was not enough, especially when I chucked it in the freezer immediately after to start cooling it down. If it was left out it may have stayed hot enough long enough to kill the bugs. You really need a 15 min+ boil to sterilise water.

I was always boiling liquid yeast starters longer so didnt have a problem there.
 

Kodos

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would you say then that Mr Malty's Calc's for pitching Dry yeast is based on Re-hydrated?
yes. Mr Malty insists on rehydration.

As far as the good Dr K goes, as much as I respect his opinion, please don't just use water straight out of the hot tap. Boil the water and let it cool to ~30 deg*. Pretty sure most tap water (especially out of old hot water tanks like mine!) is not clean enough to pitch into precious wort.


* just looked at the fermentis specs for S-04, it says rehydrate at 27 +/-3, while Danstar's spec sheet for Nottingham recommends rehydrating at 30-35 degrees. So it's probably all good!
 

thylacine

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Do you need to re-hydrate dry yeast for the same reasons that you do liquid yeast?

It's probably a good practice, but is it as important?

Apologies if this has come up before, I haven't had too much success with the search function.

"...In the Basic Brewing podcast of April 14th 2011 a request was made to participate in a brewing experiment. The
experiment aimed to determine the effect of hydration of dry yeast and the way of adding yeast to wort on lag-
time before fermentation starts, krausening, apparent degree of fermentation, the final taste of the beer and other
characteristics..."

http://hw.libsyn.com/p/1/a/e/1aeeb08f8db63...b78e6d3e3414144
 

mikec

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"...In the Basic Brewing podcast of April 14th 2011 a request was made to participate in a brewing experiment. The
experiment aimed to determine the effect of hydration of dry yeast and the way of adding yeast to wort on lag-
time before fermentation starts, krausening, apparent degree of fermentation, the final taste of the beer and other
characteristics..."

http://hw.libsyn.com/p/1/a/e/1aeeb08f8db63...b78e6d3e3414144
That's quite a report!

To summarise for the OP:
There is three tens of stuff all difference in the end result. Rehydrating introduces extra risks and processes, so don't bother.
 

Wolfy

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I could answer your question, but this question gets asked at least once every month or so, so use the search function and you can see what I said last time. :)
 

bignath

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In a perfect world, rehydrating dried yeast is a better alternative than pitching it dry. However, most don't live in that world, and i'd say that it's much worse to pitch a rehydrated yeast that has been incorrectly rehydrated, than it is to pitch dry.

If you can do it properly every single time, then go for it. If not, you're better off not worrying about it.

FWIW, i very rarely use liquid yeast as my LHBS doesn't know who Whitelabs, Wyeast etc are and therefore doesn't stock it, and i get concerned about getting it put in the post to me (minimum 450k's from nearest decent HBS), so i use dry yeast almost exclusively.

I used to rehydrate to the best of my abilities, but then did a few batches pitching dry in a side by side experiment and noticed no change/difference between the two batches (double batch split into two cubes).

No i just pitch dry, and put yeast in first, then pour my cube on top of it. I've found if i pour slowly, i get better oxygenation than dumping it in quick.
Ferments usually fire up in less than 8 hours for me.
 

Kodos

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"...In the Basic Brewing podcast of April 14th 2011 a request was made to participate in a brewing experiment. The
experiment aimed to determine the effect of hydration of dry yeast and the way of adding yeast to wort on lag-
time before fermentation starts, krausening, apparent degree of fermentation, the final taste of the beer and other
characteristics..."

http://hw.libsyn.com/p/1/a/e/1aeeb08f8db63...b78e6d3e3414144

great read, thanks for posting!
 

beerdrinkingbob

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my ales have tasted better since I started re-hydrating, I've put it down to yeast stress :party:
 

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